I guess you can still get to Leh in winter, but come on, what fun is it if the roads are all closed and you have to fly in?
I've taken the first step of contacting a Bhutanese tour company (this one) about visiting in November, and all seems well so far.
One trick: if you leave India, you have to stay out for 2 months before coming back in, unless you do a bit of bureaucratic mumbo-jumbo and apply for a permit something something. I can do that, but I'd rather not do it twice (once for Nepal and once for Bhutan) so I'm thinking, fly from Kathmandu (Nepal) to Paro (Bhutan) and only leave/re-enter India once.
That makes the whole Indian-subcontinent part of this trip look something like (using big cities to denote "sorta in this area"): Leh-Srinagar-Jammu-Amritsar-McLeod Ganj/Dharamshala-Chandigarh-Haridwar-Lucknow-uhh Nepal Nepal Nepal-Kathmandu-Paro-Bhutan Bhutan-Sikkim-long trains-Delhi/Gurgaon/Marutikunj-more long trains-South South.
Man, I love those names!
ps. Incidentally, congrats to India in the cricket last night, and good luck India in the cricket world cup finals on Friday night/Saturday morning!