What do you mean by "Reforged"?
If it is graphics, then I would say players will play both "classic" and "reforged" equally, since most people have been playing for a long time and won't suddenly turn their nose up at a campaign simply because it uses "classic" graphics. More importantly, classic graphics will probably always be better for campaigns with multiple races and techtrees because of the huge supply of "classic" graphics.
The question of classic - reforged graphics might become obsolete soon, as Blizzard may allow map makers to choose which models show for people playing "classic" and for those playing "reforged".
Now, if you are talking about 1.32+ and pre 1.32, I don't think there is any doubt about the implementation of custom campaigns back into Wc3 eventually, possibly even as soon as 1.33. Keep in mind, you can still make campaigns in the editor for 1.32+, it just means you cannot test them until they are playable.
The main issue I think is that making campaigns on pre 1.31 patches is a huge issue because everyone is using different versions, which causes different bugs when playing campaigns made on different patches. If everyone stuck to 1.26 and didnt update higher pre 1.32 patches, I think the custom campaign community would have a healthy scene for those not updating to 1.32+. But that is not the case. Even worse, in Blizzard's attempt to rush to finish reforged, they let a huge amount of bugs slowly stack up. 1.31 is the worse offender of this, but the other patches are also guily of this as well.
It is then further complicated that people who play on the same "patch" are often using two versions: the PTR of a patch or the real patch itself, which are hugely different since PTR versions were known to be seriously bugged. There is also the issue that even if players are using the same "real patch", they are actually using different versions, since they download from different people who uploaded their versions, and some of those uploaded versions have been altered by the person simply because they did something to their Wc3 game (a non-clean Wc3 folder).
So, unless everyone can agree to just move back to 1.26, the pros of 1.32+ (regardless of classic or reforged graphics) seem to outweigh the cons, especially when playing on the wrong versions doesn't always just stop players from playing--- in many cases, it allows players to play for a while, but then bug their campaign cache, missions or something else halfway through, which is the worst thing that can happen, because then players will actually think the campaign is bugged and have a negative experience of it (not being able to play it doesn't necessarily ruin someone's mood, because they didn't invest anything (time/energy) into it).