I'm not sure that was the plan.. Yes, the CD-ROM release is still the plan. Your mention of house rules being accepted by Marc is a new one to me, but perhaps I missed something before March 2008...
Sadly, the first half of your paragraph is true. In late 2006 and throughout 2007, Marc radically changed T5's vision, dropping the "T4+" (my words) view of development. Probably more significant, Marc did massively underestimate the effort required to develop a new release of Traveller by himself, and when he did get commentary, it broke down into three categories:
1. Too vague to be of use (this sux, drop in the TNE rules)...

2. Personal attacks (this document shows that Marc was never a game designer, but simply edited other peoples work)

3. Not in Marc's vision (Marc, I looked over your short notes, but decided to send you my personal design of the ultimate sci-fi [insert here: robots, fighters, missiles, gun design, et al])
And, yes, this changed in April of 2008, with my proposal of the T5 Private Access Forum here at CotI. I had come to the conclusion that there were significant issues with the direction and progress of the overall T5 effort (most notably to me, important criticisms NOT being passed to Marc), and finally talked to Marc about it (his answer was to make me part of the solution...)

o:
So, we chopped the T5 material up into logical sections (starting with Chargen), and began passing that material to those who had paid for T5 already for review. This broke the logjam, and also overcame Marc not getting details on his work problem. Also, in my view, those people who put their money out there deserved something, and making them part of the creative process hopefully did something to partially offset that.
As far as most of the material being written by the volunteers, that's actually NOT the case. Far from it (as some posters will tell you). I've made a few people mad by insisting that Marc's vision drive T5, not volunteer insertions.
And unfortunately, that detail has grown much smaller since April. I'll confess to enforcing a draconian policy of keeping T5 behind the curtain. So most of what your reading outside the private area is from someone who walked away a long time ago.
Yes, Marc could have a tragic accident tomorrow, but I am confident that Marc will finish the T5 core, and probably more. My view is, if you are curious, if you don't have a belief that Marc personally insulted you sometime in the storied past, and if you would like to perhaps have an influence in the direction T5 takes, yes, invest in the T5 CD. Otherwise, you can buy it when it is released in print form.
But, by all means, look at the Mongoose offerings -- there's much to like there... and as far as past versions, I'd recommend CT or MegaTraveller.