It would be 40 points you would lose as 20 would count for your silver status and -> 60-20=40. Effectively you had 60 points but only got 20.
If you pay for the fare now and get 20 points then of course those 60 points would count towards next year. However - the chances that you will be left with exactly 60 points needed are so low and if you do then £200 would get you up to 80 points I believe on an I fare across the pond.
If you go for it then good luck with the upgrade!