To evolve or not to evolve...

The novelty is very tempting, but hasty evolution leads to the dark side!
In all seriousness, I was having a similar thought, but decided to save my shiny togepi and rhydon for if their evolutions get a CD, well stocked on SD tyrantiar and no need for a fairy attacker.

One plus of the evolutions is evolving right now is purely novelty for the dex, few to none are relevant attackers at the moment so you wont be missing out on much in raids. I feel like of the current ones, the safe ones to evolve would be anything other than togetic and rhydon, they have special status among the sinnoh evolutions (both as fans wanting them to get a specific move and are particularly special pokemon in series as well) while the others dont fit the CD pattern for the most part.
I'd say if you have even the slightest doubt about evolving a pokemon, dont evolve it, or if you're saving for a mass evo-dex filling on a lucky egg if you're trying to get a lot of EXP.

I'm not evolving any right away because none have any great standout movesets.

Togetic needs either Fairy Wind as a new fast move or Sky Attack.

Rhyperior wants Drill Run to be a ground attacker or Rock Wrecker as a new charge move to be a rock attacker.

The others are either glass cannons or not as good as our previous legends, neither of which is immediately important for me. If we only get one evolution stone per week, then I'll just hold onto mine for now.

Don't let FOMO ruin how you like to play the game. It is tempting and probably smart to hold off evolving immediately, but at the same time that isn't fun is it? I want to get Togekiss and max it out asap, but I'm pretty sure Fairy Wind will be introduced down the line somewhere and likely invalidate it completely.

We don't know what curveballs Niantic will throw at us. However, there are a few that are pretty "safe" to evolve now. Those include Rhydon, Sneasel, Electabuzz, Roselia, Murkrow, Magmar, as well as the less Meta ones like Gigar and Dusclops. The "safe" ones will likely not get a Raid Day/exclusive move, and even if they did they'd still be pretty good. Rhyperior with Smack Down/Stone Edge will still be good even if Rock Wrecker gets released.

Trying to decide between my 93% Rhyhorn, 96% Electabuzz, 96% Togepi and perfect Magmar, since my Sneasels have pathetic IVs.

I evolved my Lucky 98 Murkrow immediately. Enjoy the game :)

It is sad that the 3h-events have made a lot of people withholding evolving .... just in case.

The metacross is a prime example of how an evolution is rendered irrelevant after an event. All metagross evolved before or after are in practice worthless. A friend of mine got a 100% Beldum the day after the event, and sighed very disappointed.

Seem like the implications to the game are not fully thought through here.