There were a lot of rumors around a quad-chip (a ultra is just 2 M* Max's) that was 2 ultras fused together but the yields were terrible and they scrapped it. I've heard speculation that they might be trying again with M2/M3's but yeah, as it stands now the Mac Pro is very lack luster.
Honestly even if they manage a quad-chip design it's still missing things professionals want (more ram, more GPU power). I'm not at all in the market for this device but I really hope Apple pulls it off. Apple is better when it has devices spanning the whole spectrum even if the edges (low-end phone, high-end desktop) don't have blockbuster sales. You sweet spot of sales is empowered by those 2 extremes and benefits from it.