In theory they should be valid as actual qualifications for the rest of your life. It would be unfair to hold you to different standards because you choose to wait a year before you apply. As far as I'm aware these will be your actual grades for the qualifications you're taking. You'll get certificates for them and they'll be the grades you put on any job applications/CV.
You've still got a while to choose whether you want to go to uni this year or not (I'm assuming you've already applied as you said you'd be applying 'again' next year), so, if it's right that most/all information regarding a-levels (and GCSEs) will be released, you'll have time to read up on what's going on before making a decision.
I will say though, there's a chance that there will still be travel/work experience/etc restrictions during your gap year. Whilst I'm glad I'm not trying to work my way through uni exams without any proper contact, I'm am unbelievably bored. I'm giving myself work to do because my work experience has had to stop (it was at a school, and they're all shut now) and I can't do any travelling (was hoping to go back to Italy and Germany, and try and get to Spain for the first time). It is possible these restrictions stay in place for a fair while. Even if places are open, they may not be willing to take on more staff than necessary. Countries may not be open for non-essential travel.