As of right now that's how I see it too. Adonis is 37 years old and still hasn't beaten anyone that I'd remotely put on a prime Spinks' level. Sergei is more formidable but again he needs to put some more big names on the board.
Stevenson at 37 is very unlikely to acquire a resume comparable to Spinks or improve enough in the ring to consider him a threat in any way for Spinks. Kovalev is still to be determined. If he KOs Pascal and then Defeats Stevenson it's going to elevate him into the conversation.
Stevenson is way back in the betting. Kovalev still has a bit to do to be held up as being at Spink's level.
If truth be told neither Kovalev nor stevenson have that many fights for men their age. Especially Adonis who is 37. Kovalev at I believe 31 or 32 still has some time. But Spinks had already fought his entire career by the time he hit sergei's age. Kovalev would be a tough fight for pretty much any light heavyweight. He started a bit late and hasn't racked up too many wins, but he's been well managed and has a lot of natural talent.
I'm all in on Kov, I think he's the real deal. He couldn't outbox Spinks, but his power and intelligent way of using it makes him a challenge for any LHW. Stevenson is awkward and powerful, but I think he's milking a timely win over a vulnerable Champion.
This, i initially thought he was just another slugger waiting to be exposed, but the Hopkins fight showed Kovalev is more than just a slugger. The guy is the real deal, as long as he keeps his head screwed on right, he is going in the right direction for being a great. But i heard Beterbiev has his number, we'll see. Stevenson is a huge disappointment as of late.