Actually, has only released approx. 15% of G1 characters in Classicsverse. I think that hardly counts as "most."
I took all the Hasbro market G1 toys and counted all the ones released under CHUGUR, not counting toys like Sea Spray and Bludgeon which are technically movieverse. I worked out that only 13% of G1 toys have been released in CHUGUR, however the G1 list I used includes character repeats (e.g. 1984 Optimus Prime, Powermaster Optimus Prime, Action Master Optimus Prime), but when including CHUGUR I also included repaints of previous moulds repurposed as Classicsverse like Springer, Roadbuster, Ratbat etc. -- but IMO they're not "real" Classicsverse. So I guesstimate that about 15% of G1 characters have been released as CHUGUR.
So there's still lots and lots of G1 characters which Hasbro hasn't touched yet. And that's _just_ looking at the G1 toy-characters... there are plenty of non-toy G1 characters that Hasbro release as Classicsverse... Hasbro has already demonstrated that such toys are possible with Acid Storm and Straxus (Darkmount). They could give us Classicsverse toys based on G1 non-toy TFs like Devcon and Arcee. And I reckon there are plenty of folks who'd lap up a Classicsverse Sunstorm or Hauler!
They could expand on G2. They've already given us G2 Megatron and G2 Laser Optimus Prime... oh, and Mindset, even though he's a repaint of Hailstorm. :/ But who wouldn't want a Classicsverse Jhiaxus or the freakin' Liege Maximo! (Rawr!!)
Or another possibility: something else entirely NEW! Not everything in Transformers needs to be based on the past... (-_-)