Do you think Dragonite/Snorlax and Blissey will continue to stay the strongest?

they won't purposely nerf them, as in "Target" them. They might change the CP formula again (they clearly stated when they did it the last time that it MIGHT get changed again in the future) and changes to the CP formula will change everything, not just those 3.
IF they ever decide to somehow add in the remaining stats in the formula (Speed and having both Def and SP.Def) then snorlax will be nerfed and blissey will be useless. Dragonite has extremely good stats, so I can't see a way to nerf him.

I think they will stay top notch but they will find a way to narrow the gap. Snorlax is likely the safest investment of that group due to balanced high stats.

No. As more moves come our way and new Pokémon introduced I think we'll find good contenders

Those mentioned mons are the ones that took the brunt end of the stick from the cp balance (something that affected all mons).

Not too long after the game came out, they went in and nerfed vaporeon (lol) but I don't think they will nerf dragonite/snorlax/blissey any time soon.

Although I do not know why lapras's stats doesn't adjust during the cp update until when gen 2 was released..