They can if they throughly enjoy the map and think it would fit into CS:GO

nope because its way to big but it may come in an operation or so but will never be an active duty map

why shouldnt it be possible to become active Duty, Cache was an opoeration map too and is now one of the most played active duty maps

Yes, every now and then Valve would release a "Operation" along with new skins but mostly, workshop maps. There is a high chance a map would be included with the list of maps highlighted in the next operation if it has a high rating in the workshop and has a balanced aspect.

Dust 3

would it be called Dust 3 Dust X or Dust Cross?

I think it would be a perfect tdm map, but its really to big for competitive. but one of the best maps i have ever seen!

I think it looks too much like Dust(2). It definitely needs some unique style. More of those nice wooden bridges, that mosque, libraries and that low river could make it look more like a unique map.
Also, I think that there are some issues with the gameplay. Especially compared with the very simple Dust2 it is way too complexe. You should always know where to go. I am not sure, but looking quickly at it, it seems like there are too many paths as well. Moreover, I don't get what the purpose of that mosque and the area near T spawn are supposed to do. There lead nowhere and are basically just areas for saving players.
Anyway, this map looks very nice and has some intersting ideas to share.