Shimano is a very conservative company, I don’t see them skipping 12 speeds on the road and do 13. And they seem pretty big believers in 2x, even their new mountain bike groupsets have 2x options (even though the gear spacing of their 10-45 cassette is identical to their 10-51 cassette for most gears). That is despite the fact that higher-specced mountain bikes with 2x are quite rare these days. (The ones that do feature 2x usually feature older 10- or 11-speed groupsets.)
Moreover, I fully expect Shimano to release only its top-of-the-line DuraAce groupset and not Ultegra or 105. Those will probably come next year.
I’d go for SRAM Force eTap, which has the best bang for the buck. Of course, they should release mechanical versions of their 12-speed groupsets in the near future, too.
Or if you want a 13-speed groupset now, Rotor is your friend. They have a variety of cassettes from 10-36 all the way to 10-52 (yes, take that Shimano, we have one tooth more than you do ) Probably for road riding, I’d look at the 10-36 cassette or the 10-39 cassette. The latter has the exact same gearing as SRAM’s 10-33 cassette, just with a 39-tooth cog added onto it. That seems like a goldilocks cassette, which should cover most needs.