Hey. I tried to respond yesterday but it didn't post for some reason. Successive landing pages is a decent idea. Try to get out and do some surveys in person too. The response rate is higher in person. My cofounder and I gathered 30 responses in the space of two hours by getting out with pen and paper. Our online survey, shared on Facebook and Twitter, got 20 responses in 4 days... not too good. Now, people who actually submit their email address are probably fairly likely to go ahead and do a survey, but there's nothing better than getting out and talking to people. Users stop being anonymous and you can put faces, ages and occupations on those you're building a product for. It's strangely motivating.

Don't say anything on the first landing page about future testing and giving suggestions. I would use that email list solely for the purposes of notifying once the product is launched. Don't send anything to those emails until after the product is launched. It's sort of "the boy who cried wolf" thing. People only want to hear from you when there's actually something they can use. Also, people hate spam and you don't want them to start blocking and deleting your emails without reading them because then they'll never know when you actually launched.

Give your survey takers the option to sign up for future surveys by having an email field at the end of the survey.