You don’t say what version of avast you have right now ?
I don’t know how long the discount offer might last - If you are/were using avast! free there is little point in waiting.
If you have an avast! pro license and this is a renewal discount, then if you update through the avastUI, then the balance of your Pro license period will be recognised.
My antivirus version is 7.0.1426. I haven’t bougth any license yet, it is not a renewal. I’ve used it for about 10 days and I’m very satisfied with it (the discount remains). I guess I’ll wait a couple of weeks more to buy it. Thanks