I am surprised that some people think that Simon don't have a chance just because Castlevania is a Konami IP. Bomberman's presence as an AT shows that Nintendo and Konami were both willing to negotiate IPs beyond Metal Gear.
Most people that used that argument was back before Snake was announced to return.
Nowadays it's generally agreed that Simon is one of the most likely Third Parties and characters for Ultimate because:
-Castlevania is one gaming's most renowed franchises (Konami's 4th best selling series, 3rd best selling if you exclude the Japan Only "Pro Kyaku" series) and while it may not be as well known as some of the franchises already in Smash, it's still more iconic and recognized than a lot of other third parties that are requested for Smash. For one, it helped define an entire style of game (the MetroidVania) and is recognized by anyone who is into games of the 3rd and 4th generations of consoles.
-Simon Belmont is the most prominent and recurring protagonist of the series, appearing in 22 Konami titles, those beign 6 Castlevania games where he is the main playable character, 6 Castlevania games where he makes some sort of appereance wheter be playable of NPC, and has been used as the main and sole playable representative of the franchise in many crossovers, such as Dream Mix TV World Fighters and Super Bomberman R.
-Is heavily associated with Nintendo due the franchise's exposure in 80's where he appeared in a Cartoon with other Nintendo characters and was heavily advertised in Nintendo's Offcial now-defucnt magazine Nintendo Power (where he even appeared in the main cover of some issues), that means a lot of fans of Nintendo consoles and Games (who are the major core audience that likes Smash) will be familiar and may even want Simon Belmont, which means people could have requested him in the Ballot by a decent or even large number (Vergeben already stated that Simon did "Suprisingly well in the Ballot") remember that this aspect is also shared with Mega Man, since a lot of people see him as a "Unofficial Nintendo Character" due to his exposure in Nintendo Systems and was one of the most requested and speculated characters for Smash 4 (and after his inclusion he had the most exposure in Smash Advertising out of all the third parties, appearing in Newcomer posters, trailers and commericals far more than Pac-Man or Sonic)
-Since Bomberman is an AT, there's literally no other Konami character that has the same profile as Simon himself, let alone a larger one than him (Goemon is only known in Japan mostly, the likes Contra and Gradius have fallen of from grace and started a hiatus way before Castlevania did in 2014, Dance Dance Revolution isn't exactly a franchise you see people demanding to see in Smash, Hudson's franchise that Konami now owns like Adventure Island and Bonk are not as iconic and prevalent as Bomberman who only got as an AT, and Silent Hill actually has sold less than Castlevania from what i have researched) and so there's really no other character from the company that would prove to be competition against him.
-Konami onwing the franchise is actually a plus, because it means they don't have to negotiate with another completely different company in order to get a character.
Really the only problem i see Simon facing is that his support doesn't seem to be as vocal as other highly requested characters like K.Rool, Bandanna Dee, Isaac or even Geno.
It could be "Silent Majority" issue (i rarely use this argument because most of the time it comes across as a Boogeyman) and that most people that like the idea haven't spoked yet.
and i say this is because back in Smash 4 speculation, Simon was always shot down as early as possible because of "1 character per 3rd Party company" , which was a fan-rule that basically turned him down before anyone alanlyed any of his merit as a character.
After Ryu's reveal in Smash 4 (which killed this fan-rule) i saw an influx of Supporters coming out of the woodwork after this event, but this still wasn't enough , and that was because there was also the whole issue with Snake's asbence that divided supporters between Simon, Snake and Bomberman (who started to gain some traction). Snake took the lead because of his veteran status, Metal Gear beign Konami's 2nd best selling franchise and therefore their second most important one, but there were a lot of doubters because of the whole Konami-Kojima debacle that blew up in 2015 and was heavily talked about in 2016.
In 2017, Bomberman became one of the most if not THE most disscussed 3rd Party character in Smash Ultimate speculation thanks to
*Super Bomberman R, which meant that Bomberman had a recent game while Castlevania and Simon Belmont didn't. However Konami's reputation made a lot of people question the idea of Bomberman beign in Smash, and there was also a lot of debate as to why would Konami give Bomberman approval for Smash and yet not for Snake's return. This lasted for the entirity of 2017, and Simon was mostly tagging along as the second Konami character that got alongside either of the other 2.
and then, in March 2018, Vergeben stated that Simon was playable. After that, talk about Simon became much more prevalent and much more recurring, and the only reason why people didn't talk more about Simon was because there wasn't a lot to talk about when it came to Smash Ultimate (remember, before E3 2018, we didn' even knew the title of the game, all we knew was that Mario, BotW Link and the Inklings were in the game, that's it) but that changed after E3, thanks to Snake beign in the game (which means Konami is now on-board with Smash again) there's literally nothing that can stop Simon, and i haven't seen a singular argument against him that holds any merit.
I have been desiring Simon for Smash online since 2013, and of all my years on this site, Simon has never been as requested or as talked about as he is now.
Something tells that a LOT of people also wanted Simon, but they dind't have confidence in that happening until now, where all of his issues are no longer present.
*This actually ended up not helping much, since Smash Ultimate's first project plan was done in 2015 (meaning that at least some character choices were already done by that point). Castlevania's most recent game at that point was Lords of Shadow 2 in 2014 and Simon's most recent appearence in any game in general was in Mirror of Fate in 2013, while Bomberman's most recent appearence was in Bomberman Live: Battlefest in 2010.