It doesn't make sense for it to happen right after hots up to the end of lotv, all they added so far points to the middle of lotv up to the end of it.
Tosh is similar to Nova but he could use Reapers and Spectres and Terran definitely needs more unit variety (could we ever have a commander that doesn't use siege tanks? Or maybe one that doesn't use Starports). If I had to guess Fenix/Talandar comes after Stukov, they have amost everything they need for him already from LotV. Rohana is a mission annoucer too so she's out just like Stetmann. Selendis is possessed by Amon during LotV, was never used or leaded a mission in the campaign and has nothing to set her apart from Artanis. Horner commands the Hyperion so it doesn't make much sense to have him.
Fenix is a purifier but Karax doesn't use them all, there are Purifier options left for him, Instigators, Adepts, Starcruisers, Disruptors, and Cybros providing global abilities?
How about Dehaka and Valerian, don't you guys think Valerian could show up as the Dominion commander?