I don't think the 17HM2 is going to be dropped. CCI has announced that that they have no intention of shutting down production.

Something to keep in mind if you are considering converting the BRNO to 17HMR. Is the bolt face flat or enclosed. If in closed you will have open the bolt face for the larger 17HMR rim. You are also going to have to move the strike further out and perhaps modify the extractor. THe 17HM2 requires no mods other than barrel lining/rebarrel.

If you do the go for the 17HM2 and it is discontinued you only have to reline it back to .22.