We've discussed this a couple time but there isn't a 'real' answer, only speculation...
I think it has its roots in two sources, CP2077 and the effort CDPR put into TW3:TWH retail box sets. As soon as they do TW3:EE they would basically have to recall all the originals. Not REALLY recall them but, why buy the old original then have to download 60GB of game from the web? They spent a LOT to make this final game really special. Gave the buyers of the various special editions and collector's editions something WORTH the cost! PLUS, the reprinting of a new EE box will cost, publishing it will cost AND the distribution will cost.
That last point all directs ones attention to point 1a from above: Cyberpunk 2077. By the end of our two year cycle, CDPR will be foaming at the bit to get EVERYone away from TW and onto the new CP2077 projekt! Also, every penny they spend on TW3 is a penny they don't have to spend on their NEW favorite baby!
However, several things could rise-up to complicate CDPR's grand plan...first, 4 mil copies sold in 14 days! IF they can sell another 4 mil by the Holiday season? I think the plan gets a little more shaky. IF they sell 90% of their physical copies in the next year...I think we will assuredly get an EE!!!
It is all about the money my friends! If CDPR can make enough cash from this cow before its time to slaughter her...they might actually do a LOT of things we don't anticipate right now. WHO knows what they will do if TW3 threatens to unseat Skyrim in less than 24 months! 4mil copies in 14 days? Skyrim only 'shipped' 7 mil copies in the first month...and shipped is not a sale in-and-of-itself does make!