I want them to fix Sims 4 first. I went through this with Sims 3. Bugs never got fixed. Eventually, they released Sims 4 and abandoned Sims 3. On the way out the door they left a suggestion to not play with all the EPs active and encouraged us to disable the packs we had spent hundreds of dollars on... That was very disappointing. Don't need a repeat with Sims 4.
Plus, there's no guarantee Sims 5 will be any better. It will take years before the game has enough content to actually be fun. If you get bored with Sims 4, imagine it as a base game again.
Personally, I want more and better for Sims 4, once I have a full working game, then they can move on to Sims 5.