Let the devouring begin!
Probably the first thing to consider is what size print you routinely make. My comments on the M8 can only be based on my experience as the owner of a Leica R9/DMR; I think the DMR is probably the closest camera to the M8 in terms of performance. Like you I shoot primarily landscape. I can make excellent 16x20 inch prints from my DMR routinely, essentially from any shot. Ignoring some issues with post-processing convenience and speed of getting the work done, these are indistinguishable in quality from prints made from my Canon 1ds2, Linhof 6x9 back, even 4x5 film. If I go up to 20x30 inches, quality starts to suffer a bit for both the 1ds2 and DMR, and this adversely affects certain images more so than others, particularly those with fine detail shot with the less well performing lenses. Here 6x9 and 4x5 still have a significant edge over both the Canon and the DMR. 6x9 holds its own against 4x5 up to 30 x 40 or so.
The M8 is appealing if you want to travel light, and the lenses are unbeatable. If you aren't going to be making 24 x 36 prints, then go that way. It is not clear to me that the new Tri-Elmarit is going to be the cat's pajamas at 16 and even 18 mm, we will have to see. Consider some of those great Voigtlander and Zeiss M lenses though, and save some money.
The Alpa seems like an odd choice, frankly. It's a bit of an exotic, and you'll find it hard to find accessories and so on, especially if you want to find something used. The TC uses zone focusing, so will be very limited in utility and adaptability. It looks like you'll be able to fit a digital back, but it will be an expensive road to take. If you want to transition through to digital that way it would make more sense to me to consider getting a medium format system camera. I think the Hy6 is going to at least temporarily resurrect the Rollei line, but that would be an affordable entry point espeicially if you are willing to consider used equipment. Same thing if you are willing to consider a Hasselblad V system. The cost of entry into the H system is a bit offputting, although if you are willing to spend 7000 on an Alpa TC, the H2 might seem downright reasonable and cheap to you. If I was going to do something as quirky as the Alpa, I would also want to look at the Horseman options--well made (maybe not to the Alpa standard, but is that really necessary?) and more affordable.
I think there is more hype than substance to a lot of the internet jibberish on Canon and Nikon lens quality. There are unfortunately real issues with sample-to-sample variation on even the "pro" glass with both systems, but some patience here searching pays off. The Canon system has difficulty on the full frame digital cameras in the wide range, especially below 24mm, but this is overblown a bit I think (note, I'm one of the instigators of the anti-Canon wide angle hype, so bear some of the blame for this). But for a bit more than $8000 you could buy a 5D with Canon 24TSE, 35/1.4, 50/1.4, 85/1.8, 135/2, 200/2.8 and have a fantastic kit. Substitute in a 24-70 or 24-105 and you'll still have comparable performance from f5.6 down and a great walk around zoom.
One consideration on the optics end would be to use a Canon 5D or 1ds2 with Leica and Canon lenses, or Contax lenses on the Canon. This was my solution to the performance problems I had with the Canon 16-35, Canon 14, and Canon 20mm, and my round about way of winding up being a Leica DMR shooter. For 12 months I had a stable system (and bank account) by using the Leica 15, 19, 21-35, and 50/2 on my Canon 1ds2. Yes, I lost auto aperture functions and had to manually stop down, but that seems sort of trivial after shooting with a view camera....