In the future, is snorlax still worth it?

Absolutely yes.

It's a hard question. It strongly depend on if Niantic change mechanic, or Stats. If that remain same, 2 Gen by itself wouldn't change much regarding Snorlax and Lapras. As well as Dragonite, but this one is attacker mostly.

Snorlax: Even if fighting types get a buff, they will still be weak to ZHB = not going anywhere on the Defender Tier List. For attack, lick+Hyperbeam will still be a gym-wrecking combo for anything that doesn't resist normal attack (and some that do).

Lapras: More steel types spell some trouble for Lapras but he will still have fewer weaknesses and better stats than most.

Dragonite: Will continue to be an attack monster, as little resists dragon. On defense, there will be more mon that can take him down; but none that will do it better than the already-available Lapras.

I can only really speak into Gen 2. And we don't know moves yet. Tyranitar will be a great counter to Snorlax. Powerful stats, possibility of great attacking moves, resistance to most of Snorlax's moves. That said, Snorlax won't lose it's great stats, so... Still a great defender. Still worth powering up.

Most definitely! Snorlax is the only mon on both defenders/attackers tier 1 lists.