I am leaving for a RTW trip in 4 months. A trek in Nepal is a primary goal, however since I won't be in Asia in Sept/Oct, I intend to do the trek in the second best season, March/April (2008). I also want to visit Tibet, which I've heard is a pain to access from the Nepalese border.
I'm hoping for some feedback on this rough route, in terms of cost (budget friendly or bank breaker?) and ease of travel:
Dec - 3 weeks - New Zealand
Dec/Jan - 3 weeks - Australia (east coast)
Jan - 1 week - Bali (possibly more of Indonesia if it will help keep transport costs down)
Feb - 4 weeks - Thailand (less time in Thailand if I spend more in Indonesia)
March - 4 weeks - Nepal
April - 1-2 weeks - China/Tibet - fly from Kathmandu to Chinese city, such as Chengdu, then take a train to Lhasa, Tibet (this way I can access Tibet with an individual Chinese Visa, vs with a tour and group Visa from Nepal)
April - train from Lhasa to Beijing, and down east cost
May/June - SE Asia - Vietnam, Cambodia, Thailand (time in Thailand will depend on how long my first stay was earlier in Feb)
July - India
Aug 08 until the money runs out - Africa, Europe, South/Central/North America

From your last sentence, I take it that time is not an issue for you. Is it at all possible that you could extend your travel until the prime trekking season in Nepal in October/November? That way you could rearrange your trip to go to India first, then SE Asia (not Indonesia), NZ, Australia. In July, August, September you could be in Indonesia, China/Tibet then into Nepal by October. The weather patterns would be much better on the whole for you if you did the trip in this order. Also, in terms of money this itinerary might be possible as the only expensive places you will be in are NZ, Aus and selected parts of China. How much are you planning to save for this trip?
I don't understand, why not go from Bali to Singapore, KL to Singapore and then on to China. Travel from China into Tibet to Nepal and into India. From India take a budget flight to Bangkok and visit the rest of Mainland SEAsia. I suspect that this routing would be much less expensive than flying from Thailand to Tibet and then flying Nepal to China (in fact, I don't think there are many, if any, flights from Nepal to China).
This would also delay your entry to Nepal to better time weatherwise.
I would definitely recommend that you take a look at the following budget airline websites to help in planning:
which budget,
flybudget,
cheap0,
europebyair.com,
Air Ninja
openjet, and
asia budget airlines
Ruth
Sataraman - thanks for the feedback. I'm going to have about $25,000 to dedicate to the trip (covers everything from insurance/storage to transport and per diem), however I'm fairly intent on making it to Africa, Europe, and South America, and I'd be worried that I wouldn't make it so far if I get hung up in Asia through Fall 2008. I'm willing to take the second best time of year, which I've read is March/April (before the monsoon). The potential money I can save through couchsurfing could alter my approach though (or just allow me to buy more beer!).
My budget and itinerary is online.
Everbrite - thanks for the ideas. I think it'd probably make more sense to take the approach you're suggesting. I was thinking I might get caught up in China as it's so big. I've spent no time learning about the place, though I do know it'd make sense to hit the big cities like Hong Kong, Shanghai, and Beijing, and then take the train to Lhasa. Also, I have a friend who calls Chengdu home now, so I could always stop off there along the way.
I try not to let myself get frustrated trying to plan, as the trip is all about freedom. I really don't think I can go wrong (however the more efficient my approach, the longer I can stay abroad). :)

My suggestion: After February, fly Thailand-Nepal per your original plan. Fly Nepal-Shanghai (if you already have a Chinese visa) or Nepal-Hong Kong if you don't. Royal Nepal Airlines has these flights on their schedule although they are only 2x or 3x per week. The flight to Shanghai is actually a stopover on the KTM-Osaka flight. Not sure how reliably these flights are flying, but it is the only option on the books right now for going directly Nepal to China. From either Shanghai or HK, explore China throughout April--put Beijing in this part of the travel--then go to Tibet then back through southern Yunnan part of China to SE Asia. You may find that you want to extend the China/Tibet part into early to mid-May and chop a couple of weeks off SE Asia, but you can play that by ear.

$25,000 is a good amount of money. In most of the places you listed in your original post $30 per day would not be a restrictive day-to-day budget. If you divide $25,000 by the number of days in December - August you get $92 per day, so that suggests that you would be able to travel well beyond August '08. You should definitely be able to fit in Africa, Central/South America, etc.