SMRPG didn't go away as it did "evolve" into Paper Mario and Mario and Luigi RPGs. I consider both spiritual successors in their own way with the Mario and Luigi games being a lot closer to the original vision, especially with Yoko Shimomura still composing the music for the games and their wicked sense of humor. I don't know what exactly happened with Paper Mario. It's not like anyone asked for it to be made into a platformer and then an RPG with no partners and boss battles that last 20 days apiece. TTYD took everything that made the original Paper Mario good and made it better, like a sequel should. Super Paper Mario tried to reinvent the wheel and Sticker Star clumsily tried to go back to the original formula while embarrassing itself in the process.
I'm staying optimistic on the next game in the series.
I will bring the same evidence i bring everytime I talk about the possibility of a fifth game on the WiiU it's there:
http://nintendoeverything.com/intel...-unannounced-wii-u-title-on-linkedin-profile/
This happened on September 30 2012 which means that we have a good chance to hear about it this E3. This game maybe a paper mario one since getting a game on the WiiU is likely anyway.
So now, let's see the progression of the series (note: this is the general opinion I hear but it's the most accurate i heard and it may differ from your own).
PM64: awesome game
TTYD: This is a masterpeice and it made the original better
SPM: It doesn't follow TTYD which is disappointing but it's not that bad either
Sticker Star: Really bad ESPECIALLY because of the removal of all the rpg elements that made the first 2 games awesome.
I can understand that they wanted to try something different for spm which didn't turn out to be bad but sticker star is where it begins to feel annoying.
However, I noticed one thing: the game was released a week before the wiiu was released. So, when the development started, the wiiu was not ready so, they choose the 3DS. Indeed, this means that they changed the experience to adopt this model like for example, segmenting the game in a world map instead of an overworld.)
For the story removal... I agree this one is weird they chose to not put a story because acording to club nintendo survey on spm, people didn't want that. If I look at the text of ttyd, I have to tell to myself that this method was unreliable but today, miiverse exists and I have the feeling that they put it to know what people want. Also, I would be pretty surprised that nintendo didn't acknowledged that they should do just like ttyd today.
All this to say that I beleive that if the next is on wiiu that we may see rpg elements back and of course i would be VERY happy about it. Also, I just imagine that if indeed a paper mario game is announced at E3, we may see a paper mario reveal for ssb4 (yeah he has "some" chance but I like daydreaming).