A few moments ago, Nintendo announced that StarTropics was getting released on the Nintendo Switch Online app. Will this rerelease be allowed for runs?

Of course it will be allowed if there is no major difference. So far, all rerelease of the game were correct, so, it is most likely going to be fine.

Will it be added to the platform list?

I just tried the Switch re-release and I was thinking the same thing: is there any chance for Switch to be added as a platform for the submissions?