I don't think it is reasonable to get more than two emulsions made from one company in 70mm ever again, unless you're talking about actual aerial film.
I think it would be better for Ilford (as apparantly Tri-X is still available here in the states) to offer something in this size that Kodak doesn't.
Don't get me wrong. I shoot 2 1/4 x 2 3/4", so it's not as if I have a problem with older emulsions in this size, just that offering Delta 100 and 400 instead would give Ilford an edge over Kodak's offering and possibly encourage more people to flip flop or encourage people that aren't fans of Tri-X to give the format a try.
I definitely think this format would appeal to all of the people I see (at least on here, never met one personally) who gripe about Ilford's only supplying 120-sized film.
You can cram 65 shots in a 70mm cassette, more than three rolls of 220!
If Kodaks is any indication though, it would be best to consolidate to just two, maybe just one emulsion. Delta 400 would definitely be my choice over HP5.