Bing probably won't win....

but that doesn't mean it can't, particularly if google are stupid.
I can think of a number of top tier companies, 3dfx for example, who were the absolute unquestioned masters of their market but who got wiped out because they didn't take their competition seriously and let their product stagnate.

Google almost certainly isn't running around in a panic over Bing, to wipe them out now would take a product which is measurably better in some important way(speed, ease of use, quality of results, etc) for anyone to even come close to toppling them. At the same time they'd be idiots to ignore new competition, inspiring the dominant market players to expend resources improving their products is one of the most common benefits of increased competition.

Google are just being sensible. Bing may be nothing in fact it almost certainly will be, but it may be something. Even if it only grabs 1% market share, if it grabs that share from google they lose money.

Only stupid companies blindly assume that their competition will fail and their dominance cannot be challenged, and Google are anything but a stupid company.

google susceptibility to SEO gaming is significant

On the one hand, the lack of a technologically compelling competitor to Google concerns me. As a consequence, google susceptibility to SEO gaming is significant, but Google doesn't have a sound business justification to change what is working unless a competitor outdoes them. Unfortunately, in business the only 'justifiable' time to fund improvements is when there is *something* to gain and Google simply has nothing to gain in this context without competition.

On the other hand, I don't think Microsoft should be the one to come in. They are another goliath that retains some good technical people, but strategically knows little more than brute force nowadays to get into markets. They bought their way into second place in game consoles, they are trying to buy their way into some niche markets where Linux currently leads (both in the server room and embedded spaces). They tend to offer generally 'mostly sufficient' technology that doesn't really stack up to their competition or blow them away on a technical level, but earns what ground it can by sheer force of money earned through the markets they did corner at the right time with the right technology (invented or purchased). Through dumping (and even further, sometimes essentially bribing customers to use their products) they pursue an obsessive need to take over new markets.

In other words, I want to see Google challenged by a competitor on the strength of the technology they offer, not on the strength of a massive marketing budget and the ability to blatantly lose money for future market share. I have tons of respect for Google for actually innovating and revolutionizing search while every major player languished. I want another google, not microsoft, to get Google back on its toes.