It could be another SARS and not amount to much, or it could be much more serious. Given the limited flow of information from China and Russia, it's hard to know for sure how the situation is developing. As the extreme position, some have specualted it could (or already has) recombine with Ebola to make a highly fatal disease, much more fatal than the 2.5% fatality rate for the Spanish flu in 1918. Aparently there are some similarities between H5N1 and Ebola that make this possible, but I'm no genetic scientist, so I can't really assess this kind of speculation.
Carl