+1 You can distortion on the VC, but much less so on the WATE.
If it were me I would do the following.
Try to get an upgraded M8U for a really good price. From what I am seeing folks are beginning to get silly about pricing this wonderful body in hopes of getting an M9 with a lot of the bill already paid. I believe you can get the M8u for something in the neighborhood of $2500 which if true is a wonderful bargain.
Although I do not think the UV/IR cut filters are a necessity on the M9 I do believe it performs better with them. Thus I don't think looking at filter cost is a critical item when comparing the two. I have an M9 with a spare M8u and use the filters on the lenses for shooting both. But the file IQ is sensational on both so the biggest issue is that you can now shoot very wide without going to extreme WA lenses like the WATE. A 21 elmarit on the M9 now feels like a very wide angle lens (which it is).
Having the sapphire cover on the M8u, along with frame lines optimized for 2 Meters instead of 0.7 meters is again great. I think you will come to know and believe in the frame lines for the M8u. Sad that Leica didn't think the advantage was great enough to carry forward to the M9.
Both the M8u or the M8.2, along with the M9, are just stunning performers. But you need to be sure you like and can handle focusing the DRF's from Leica before stepping up to a new M9. You can read all of the forums (fora?) and see folks new to DRF's that immediately fall in love with them and then those others who, after trying them for a few months simply can't get it right. No sin in that as we all have decaying vision. Even I, an inveterate M shooter from the 1960's have days when the hit rate due to focusing errors makes me wonder if I am now getting far behind the M issues. However, because of weight, size, and delicious file quality plod onward in hopes of recapturing my youth. If you find the M DRF's are absolutely for you, you are unlikely to lose any (serious) money reselling an M8u. However if you should buy an M9 and then find you must resell because you can't use it, you would likely lose at least 20% on resale (.2x $7K = $1.4K!...ouch).
So you now know my position. Your position may vary so move carefully. I wish you well and anticipate you will love the M system unless there is something unforseen that happens. I am 72 years old and so far there is nothing that would make me abandon my M9 and M8u. Perhaps in a year or five but who knows. (or cares) When I am 75 or 80 these issues become moot. At that point I will have written off the investment and enjoyed a number of years with the wonderful cameras.
As you are well aware, the investment in the Leica systems, M or otherwise, is not a trivial one. But if you have enough time to have written off much if not most of it, you are financially solid and have had the benefit of the best of technology for 3-5 years. Wish my HiFi system had this kind of track system!
Thanks for listening. I am keen on continuing to listening to such dialogue so i can determine, at age 85, to the logic about whatever to buy at that age.
All the best to all the shooters
Woody Spedden
Fort Collins, Colorado 80528