Some Questions About Nikon Lenses

Some newbee questions:

When Nikon offers a rebate on a lens, is it generally an indication
that the lens might be discontinued or that a newer/improved version
will be out soon?

Do rebate offers pop up all through the year or just at year end?

How often do the lenses get upgraded/improved?

I'm thinking specifically about the 80-400 VR lens. Reviews were
generally good with some reservations about AF speed etc.

Thanks.