1 Million users.. I can't Scale!!

[yoda]

Hi guys,
My situation is as follows:

1)I've developed a service that generates content for a mobile service.
2)The content is sent through an SMS gateway (currently we only send
text messages).
3)I've got a million users (and climbing).
4)The users need to get the data a minimum of 5 seconds after it's
generated. (not considering any bottlenecks external to my code).
5)Generating the content takes 1 second.

I'm considering moving to stackless python so that I can make use of
continuations so that I can open a massive number of connections to the
gateway and pump the messages out to each user simultaneously.(I'm
thinking of 1 connection per user).

My questions therefore are:
1)Should I switch to stackless python or should I carry out experiments
with mutlithreading the application?
2)What architectural suggestions can you give me?
3)Has anyone encountered such a situation before? How did you deal with
it?
4)Lastly, and probably most controversial: Is python the right language
for this? I really don't want to switch to Lisp, Icon or Erlang as yet.

I really need help because my application currently can't scale. Some
user's end up getting their data 30 seconds after generation(best case)
and up to 5 minutes after content generation.  This is simply
unacceptable.  The subscribers deserve much better service if my
startup is to survive in the market.