So, it looks like this:
1. Boeing can go on with 747X. Even if it is a niche aircraft, it will be financially successful because of not high development expenses.
2. Boeing has time to wait and see how successful A3XX is and what the superJumbo market really is. The worst (for Boeing) possible scenario is if there is quite a large market - but it is filled by the product that was first (A3XX), and there is no space for new VLA at least until new generation VLA is required. Other possibilities: A3XX itself is a niche aircraft that is a real disaster for Airbus (similar to Concorde, but I'm absolutely sure Concorde is a greatest aircraft ever built so it had to appear even by such a price - I am not a British or French taxpayer though
); or A3XX is really successful and the VLA market is big enough another superJumbo to be developed.
3. (fantastic?) In 1969 Europe made SST and Boeing made Jumbo-jet. 40-50 years later Europe made very advanced, really new generation superJumbo (isn't A3XX supposed to be one?) and Boeing develops new generation SST that is rather economically viable. Needless to say, if there is a discussion about VLA market, the SST market is potentially huge and depends only on possibility to create an aircraft not THAT expensive both to develop and fly.
4. Of course, no way for Boeing to develop both VLA and SST. Only with subsidies from government (I mean REAL subsidies for these developments, not that rubbish I saw here several times like "Boeing gets subsidies as the government pays for military planes",...). I am a US taxpayer now and I AM AGREE