I've seen similar comments like this on other threads from you, but... the way you're wording this I think is very bad. I don't think people will just suddenly stop supporting Isaac after supporting him so long, or any other characters for that matter. You can still support a character even if you think the character is unlikely. I still support Isaac, I still support Lip, I just think Isaac still has a fairly good chance (around 60%) and Lip I just think is abysmally low, around 20% at this point, even though I really want both of them.
Some people just don't want to get their hopes up. For me, with Isaac, the lack of seeing him so far is what makes me believe either he's playable or potentially being saved for DLC. Some people say that his lack of being shown as an AT means nothing, but honestly, I think that means literally EVERYTHING for Isaac. He should've been one of the first AT's to be confirmed... if he was still going to be an AT.
And Shulk, a character with a small history with Nintendo and likely isn't going to appear in future games, is in while Isaac has far bigger history with Nintendo, his games sold better, and has been requested a lot longer. Shulk got the treatment now that Isaac should've gotten in Brawl, really.