FUD Zilla claims the half year delay of the GF100 "Fermi" will not hinder the introduction of mainstream Fermi graphics cards. The site writes a batch of mainstream models may arrive in June.
Entry-level is where the money is, even though you need to send millions of these cards to make a decent profit. Mainstream Fermi is a project that Nvidia is pushing side-by-side with high-end Fermi and we've learned that mainstream Fermi should be on time.
You should roughly expect it one quarter after the first Fermi, and if all goes well June should be a good month to launch. Since Nvidia changed quite a lot of plans in the last few months, don’t be surprised if it launches a bit later.