I might be overly optimistic, but I think they’ll be adding things with every patch. It might just not be the massive surge of new stuff we got with the Shadowlands launch. They might just focus on two to four races at a time, and I don’t know if I’d think Allied Races will be getting anything in 9.1.
I think 9.2 might be a more realistic point to see stuff for Allied Races, just because core races still need more work. That said, I don’t know how the devs prioritize these additions, whether or not they try to make things, “fair,” by working on an equal number of races from each faction, or trying to bring some races up to others, or just throwing that all away and focusing on adding stuff players ask for regardless of faction or which race is lacking or has plenty of stuff already.
Either way, I’d say to the OP, if they have stuff they want to see added for Mechagnomes, then they should start a thread with the request, examples, visuals, etc… There’s a really good thread done for new Worgen stuff, for example, that does this.
There’s also a good one done by the San’layn community.