This free upgrade is not just for this new promo,it is open to all existing UniFi customer from day 1 too as long they are

-registered before 31st Dec 2016
-not receiving any free upgrade before within this year (pay the same price but increase speed)
-is subscribed to VIP 5/10/20 or UniFi 30/50 (whatever the variants)
-the area can support the new upgrade speed
-not under special scheme when buying a new home with UniFi ready
-not a business customer
-no contract refresh
-existing UniFi 50 to 100 only may or may not need to change their CPE (BTU and RG) with no charges.
-no retail price change for 2017 for newcomers.

So they will have a list of eligible customers and these customers will be contacted in stages if interested or not in proceeding with the free upgrade.You will be contacted via email,telephone or SMS.

5 to 10
10 to 30
20,30 to 50
50 to 100
100 - unchanged.

here.

https://www.tm.com.my/speedupgrade/Pages/as...Website_Eng.pdf

so far we only know that unifi advance 30 will have speed upgrade to 50mbps, while advance 50 will have speed upgrade to 100mbps.

we could only speculate that the other streamyx/unifi package will be upgrade as per below:
streamyx:
384kbps -> 512kbps
512kbps -> 1mbit
1mbit -> 2mbit (or webe if the infra doesnt allow)
2 mbps -> 4mbps (or webe if the infra doesnt allow)
4mbps -> 8mbps
8mbps -> no upgrade (unless unifi are supported, maybe unifi 30 advance plan)

unifi:
5mbps (vip5) -> 10mbps (vip10)
10mbps(vip10) -> 30mbps (unifi30 advanced)