As of right now, the only Intel desktop chips that are 32nm are Gulftown (6-core, LGA1366) and Clarkdale (2-core, LGA1156). Unfortunately, the 45-nm to 32-nm transition is gonna be on three seperate platforms so let's try to go through the options:
The LGA1366 platform, on which Bloomfield (original 'Nehalem' chips, such as i7-920) and Gulftown are based, should be around until at least the end of 2011. As of right now, you have two options on this platform: quad-core, 45nm chips, or hex-core, 32nm chips. It might be possible that they release a quad-core, 32nm chip, but I haven't heard any rumors or seen any roadmaps that indicate that this is gonna be the case. So in this route it might be possible to upgrade to a quad-core 32nm processor, if they ever release one.
The LGA1156 platform is what's used today for the 32nm Clarkdale chips (2-core) and the 45nm Lynnfield (quad-core) chips. Again, each chip only satisfies one of your requirements (either only 32-nm or only 2-core). Again, it might be possible that in the future, they release a 32-nm quad-core, but I haven't seen any roadmaps or heard any rumors that support this.
The only guaranteed Intel 32-nm quad core processor platform is...not released yet. That will be the LGA1155 platform, which will be the first platform for the new Sandy Bridge series. This will be 32nm, quad-core, hyperthreaded, and have an integrated graphics controller (one that supposedly has cache coherency with the CPU core...cool?). This platform will predictably not be compatible with current chips, so no chance that you'll be able to throw these processors into a motherboard you buy now.
So if you need 32nm right now, you're gonna have to either spend $900 on a 6-core LGA1366 processor, or only get 2 cores on an LGA1156 procesor. If you can wait out until the end of the year, you'll get your quad-core 32nm processor on the LGA1155 platform. I don't know if overclocking is important to you, but I've heard rumors that they're gonna seriously limit overclocking on this platform, as it is supposed to be a 'mainstream' platform. You'd have to wait until the replacement of the LGA1366 platform to get serious overclocking with lots of 32nm chips (unless you pony up for Gulftown right now)
One last thing: the only platform right now that can support both 45nm and 32nm processors and have 4 or more cores is the LGA1366 platform. Unfortunately, you either get 4-45nm cores or 6-32nm cores, so actually power consumption is the same. Of course the 32nm cores get multithreaded jobs done faster, but if you're just looking at it at a rough 'which generates less heat' standpoint, they are both at a wash right now...unless they come out with a different processor soon...