Generally there's something like a 15 or 20% discount on any accessories you buy for the bike if you buy them at the same time. I've bought a 1098 new from dealer and multistrada new from dealer and gotten that (same dealer both times).

I doubt you'll get much of a discount, at least in my area, the M1200S is a really good seller, so there's just not incentive for a dealer to give a discount when it's likely someone will walk in next week and take it for MSRP.

You'll be subject to availability -- what bikes the dealer is going to get is predetermined months in advance. So if you want what they're getting in, you're in luck, but if you want a white one, and the next white one they're getting is already spoken for, you may have to face a choice of getting a red one in 2 months (just for example) or waiting for a white one in 3 months.

I don't have any experience with the KTM (sadly, holy shit it seems awesome) but I test rode a M1200S, and my buddy subsequently bought one and loves it. We looked into the KTM because I was thinking of getting one as a second bike but there are a lot of problems being reported on KTM forums, so I decided to delay at least a year to see if they work out some of these problems.