I think any upgrade is directly tied into a significant drop in price for the drop in part. In other words the price of a Red XP-E2 would have to be much lower then the XP-E price is now for it to be, and I hate to use this phrase, worth A51s while. If the price of an upgrade kit is almost the price of a W90 would you want the upgrade? Plus what's an XP-E2 have like a 10 to 12% bump in output. Not much of an upgrade there more of a retro fit. Maybe in a business sense he should have some upgrade kits available from time to time for word-of-mouth/advertising/promotional reasons at least but Jeff's secret is getting a great price from his vendors and until he gets that magic price the only answer your gonna get is "soon" I bet. Then again he may be rolling out an updated line soon and maybe he'll have the stock to do the upgrades.
Would a fat discount on his latest models be worth an upgrade?