From experience, I'd say the best answer is NO, you won't be able to run your 32-bit applications.
When I upgraded to Vista, I went straight for 64-bit version of Vista. Then I learned the hard way that half the software I owned wouldn't run on 64-bit vista, after upgrading from Windows XP 32-bit. Well, every application I owned WOULD work, but...
I had to either upgrade the version or replace it with a new version. And of course, every upgrade or new software package was really expensive.
So I had to down-grade to the 32-bit version of Vista to get all my software to work. That was Vista Home Premium 64-bit, and then back down to 32-bit.
But then the other side of the story is...
Since I went back to school, I qualified for the student discount from Microsoft. So I got a decent deal on Windows 7. I had a choice between 32-bit or 64-bit. I decided to go straight for 64-bit. Yeah, I knew I had some 32-bit software that wouldn't work on 64-bit Vista. But the hardware is very up to date (very) and it seems silly to run a 32-bit OS. So I decided to just REPLACE any older software that wouldn't play nice with a 64-bit OS.
But after I upgraded to Windows 7 Pro 64-bit, I got a nice surprise. All of my 32-bit software applications would install AND RUN fine on Windows 7 Pro 64-bit. The only catch is, I had to set some of them to run in a compatibility mode (comes with windows 7 PRO only) so that the OS would appear as "Windows XP SP3".
So based on those two experiences with 64-bit software, I'd say if you want to go 64-bit, you'd better go straight to Windows 7 Pro. That way, it's more likely that your older software will work.
Note I can't guarantee all your 32-bit software will work on Windows 7 Pro 64-bit. However, it is much more likely to run on Windows 7 Pro 64-bit than it is to run on Windows XP 64-bit.
If your hardware can handle it, go straight for Windows 7 Pro.
Oh and if you are doing high definition video editing, you're probably someone who would benefit from switching from 32-bit to 64-bit. At least then, you'd be able to access more RAM, which would be helpful.