A few thoughts:
- 6000 registered users in a couple of days is hardly going viral. It's a promising start but too early to use that adjective (and the numbers are also pretty low).
- The fact that you are trying to sell something you worked on for more than a year just because you can't keep up with the email volume is... suspicious. Especially if the income estimates you give in that article are accurate. Why not just ignore your inbox for a few weeks and come back to it later?
- I think the answer to the question above is obvious: you know your success is temporary and you're trying to cash out while you can. Sorry for my cynicism, just being honest.