Temporarily changing the domain name?

I host a large website that gets many visitors from search engines, but I need to host it on other domain for about a year -- during that period every page (except the main) will be redirecting users to appropriate page on the other domain. For example:

www.mydomain.com/page.htm ==> www.newsite.com/page.htm

After one year, I'm going to set everything back to the previous state (mydomain.com will no longer redirect to the other one). How this will affect search engine popularity of www.mydomain.com?

Why would you want to do such a thing? If you use a 301 redirect, the new domain should replace the old domain in the SERPs.

But, any new "natural" links you obtain in that year span to the new domain may be wasted opportunity when you switch back. You will need to set the 301 on the new domain and contact everyone who linked to the new domain (or changed their links from the old domain) requesting a change to the old domain. Clear as mud?