I will do Dawnguard questline so I will use crossbows, but now I am stuck by not knowing can I put perks into archery?

I think by the time Dawnguard comes out for PC, I will either have made a new character (the one I have now is at level 128!) or picked one of my old characters, especially since it seems likely this DLC will have two branches.

I suspect that crossbows will fall into archery. I don't see why they should create a new perk tree for this.