@You rock,
I believe it takes longer now for new-joiners than it took the first two years until today. We have pilots that started as FO that have already upgraded to RCA and now upgrade to CPT. This is possible because there is a seniority system, and Norwegian is following it. No exception.
My guess, if you join now as RCA, is that it will take at least three years. But I can be wrong. Can be less. Upgrade is strictly based on seniority, and for internal CPT upgrade you'll need 6000 hours of which 1000 on wide body. Until now, about 50% of all pilots that can upgrade (i.e. all FO and RCA) have already upgraded. Norwegian takes good care of their pilots in that sense. Well, that's what I believe anyway. Other operators stop upgrades and only take direct entries. Norwegian on B787 fleet has minimized direct entries on behalf of internal upgrades.