i cant say if they will ever lower the requirements, but i can tell you that you wont be able to download Ideas to a device that doesn't support the requirements. The Android market won't even let you see the app.
i started an idea request for them to lower the screen requirements. If you want them to add this we need support. So vote on the thread and cross your fingers.
Here's the link to the "idea" thread that you can vote on.