The whole reason why those eight guns only had a single variant to boot was to keep "class equality" among the four main kits.
Now, it's to be seen if these new variants are going to be free for everybody, exclusive to Premium players, or updated to their respective, individual DLCs.
If it's one of the first two, I can then actually see DICE adding at least two more new guns for both Medic and Support down the line (four total). Now, if it's the last, then DICE may "need" to add a new Scout rifle to TSNP and a new gun for Assault in Apocalypse, bearing in mind any added main kit primaries will come with two variants each. In that case, then DICE would need to additionally add three new Medic and Support guns among the already-existing DLCs to make sure all the main kits get equal treatment. Note "main kits," as DICE hasn't added a new Pilot/Tanker gun in either TuTi or Apocalypse, and it's possible for those positions to also be filled. Meanwhile, ITNOTT came with two handguns, and Apocalypse came with one. So, it's even further possible that we may also get upwards of five new handguns (potentially including the already-existing Howdah Sweeper and C96 Export), two handguns for each DLC. Of course, the Pilot/Tanker guns and handguns would be assuming DICE would try to equalize the amount of (bring-back) content all the DLCs come with, which should honestly be standard if all of the DLCs are asking for the same price if bought individually.
So yeah, we may potentially be seeing anywhere from four to fifteen new guns within the future. Although, I could honestly settle with the likes of eight new guns (one for Assault, one for Scout, three for Medic, and three for Support), or ten if the Howdah Sweeper and C96 Export are brought to retail (with whatever rebalance they may or may not need). That would probably be the sweet spot, in my opinion.