They are only issuing 75,000 stikers.
I have one now on my 2004 HCH.

I am considering buying a 2006 HCH but maybe not till well into next year.
But what if all 75,000 stikers are gone?

Can I take them off my old car and put them onto my new car?
(Of course they won't come off cleanly, I'd have to get new ones and probably prove to the DMV that I removed the old ones maybe by sending in the remnants which have a unique number on them.) So the DMV would have to send me new ones.

In other words, do they belong to me or to the car?

 

I'm sure they belong to the car, but I can't guarantee that. At the very least, they'll increase the resale value of it.

 

I imagine it's the same as when I got the white stickers for my RAV4 EV. You get a certificate along with the stickers, documenting that the DMV has issued stickers to THIS car. If the highway patrol stops you they may ask to see the certificate as proof that the stickers were issued to the car, i.e. that you didn't steal them or something. The stickers definitely belong to the car.

 

At this point there are only 3 models that qualify for single-occupancy HOV lane. Since AB2628 has just passed recently, I am sure that is the reason for the surge in applications. I believe the latest count was 36,000. From this point I would imagine you have some time before they run out.