@Dex Stewart
Gave him to Pipp as a gift?

@Christopher Forrest
Could they do that? Yes. Will they do that? Perhaps not. After all, the showrunners want the audience to focus on the central Mane Five cast, and they don’t wish to become too reliant on cameos in the series (not to mention Spike wouldn’t be voiced by the same VA either way, as that had already been established). If Spike and the other dragons don’t return, I am sure there will be an in-universe explanation for that (likely that they were wiped out in a cataclysmic event, something that makes sense considering the Alicorns were also wiped out and magic completely disappeared).

But let’s just hope spike is still in his young adult age because dragons can live for thousands of years

@Christopher Forrest  
I assumed he’d still be around because he’s a dragon, and it’s established they live for centuries.

I have a theory that spike might be still alive. My theory is that chrysalis,tirek and cozy glow escaped their stone prison and killed twilight in a big battle and spike trying to save equestria has lost many of his friends and loved ones in a tragic battle he sacrificed himself like how the pillars did. by trapping the legion of doom and himself in stone but it was to late chrysalis manipulated the earth ponies,Pegasus and unicorn into dividing. So out of anger and pain of losing all those around him he turned himself and the legion of doom to stone for centuries.

Sunny either didn’t like Spike,and threw him away, or loved him so much he got worn out!