I also have an M6. The M6 isn't completely gone ... yet. (posted on 2/14/2017 in Whites Electronics forum by spokesman) "White's is continuing to build the M6 by special order, so long as demand remains reasonable. However, no advertising."
Someone on another forum claimed the MX5 is in the same 'being discontinued' category but its still shown on the White's website.
The Whites website shows they are bundling some nice items with their detectors, here is the current lineup and MSRP starting at the bottom:
CoinMaster $230
TreasureMaster $300 (comes with PinPointer)
TreasureMaster Pro $450 (come with PinPointer)
MX5 $600
MXSport $850 (detector only $800)
MXTAllPro $900
GMT $900
Surfmaster PI $900
TDI SL $1200
VX3 $1200
V3i $1500
V3i wireless $1800
I think the M6 MSRP was $700, so the nearest replacementare is the MX5.
If they discontinue the MX5 they will have a significant gap in their line unless it is replaced by something new.
Compared to the competition, White's pricing structure looks expensive.