Just bought the 2016 29MV!
Well since posting my questions here, I went back to the dealer and checked out all my concerns. The wheelbase is 223" (I measured it), the radio says SiriusXM on it so I should be able to hook it up somehow. The outside cargo space is less than I had before, but I put too much stuff in my 2004 Greyhawk. The older Greyhawk has "basement storage" which means there is a large step up from the driver's seat to the floor and the ceiling height is just above my head (I'm 6'2"). The ceiling height on the 2016 is 84" which gives the appearance of much more space. The 2016 has more interior storage. I drove the unit I am buying and it rides great so far. I will pick it up late next week. I chose the exterior Vanilla color over the special paint option because 1) it costs much more (about $5000 to $6000 more), 2) I believe the lighter color will hold up better due to UV causing fading over time, and lighter exterior colors absorb less sunlight than darker colors and so it should be cooler during the summer. The dark paint looks very nice, though.
The new Greyhawk has a fiberglass roof, auto leveling, new King Control Jack antenna that doesn't have to be raised,solid surface kitchen countertops, a thicker foam mattress that is NOT a Denver mattress, Furrion brand TV's and MCD roller shades , a 1000 watt inverter. Many of the windows are larger including bathroom, cab-over bunk side window, side entry window and the dinette window looks larger to me. The flooring is a wood plank pattern vinyl except under the dinette and in the bathroom. The shower stall is larger than my 2004 Greyhawk's. The water heater is tankless. The hitch is rated for 7500 lbs with a 750 lb tongue weight. The windows are frameless and are tinted fairly dark. The only options i bought were slide toppers and Maxx air covers. I will post photos when I bring it home.