ETA NOW
You do not require the 50 hours cross country to get an instrument rating added to your FAA private certificate.
If you graduate from a FAR Part 141 approved IFR course you are exempted the 50 hour requirement.
I am 100% sure of this because I am closing in on my IFR checkride and have checked this out with both the flight school and the examiner. FAR 61.71 is the relevant rule
You will require the cross country time if you decide to get your commercial licence but already having the IFR rating gives you the option of building IFR cross country experience into the flying that you will already be doing any way to get your commercial certificate.
The commercial requires a long cross country flight that must be conducted in VFR conditions (on an IFR flight plan if you wish as long as the weather stays VFR) and also a dual cross country
which must be in VFR conditions, if you already have the instrument rating you are free to do the balance of the 50 hours required in IFR conditions.