We're launching a redeveloped site soon. Google has already indexed the site that we're going to replace, but the links that google indexed are no longer applicable, because the new site has a totally new routing scheme. We have new sitemaps for the new site. Is it possible to get google to re-index the new site, or do we have to wait until it gets around to it?
Because you've created a sitemap you can register with Google webmaster tools if you haven't already, and then submit it. (Site configuration -> sitemaps.) This doesn't guarantee anything, but increases your chances.
You should also map older URLs to new ones using 301 redirects.
Another option not yet mentioned is to increase Googlebot's crawl speed through Google Webmaster Tools. This will get your pages indexed more quickly - though of course it won't make the pages rank better.
Well, you could create new sitemaps with new names that Google is not aware of, and register them in your
robots.txt or submit them in Google Webmaster Tools. You would surely get the web crawlers attention, which are the gateway to indexing, but you cannot force the indexing of your pages. If web crawlers don't visit your site often, this is a solution.
If you can set a canonical link from old pages to corresponding new pages, that might help too.