Maxis: launched Jan 2013, smartphones April 2013 [3 months]
Celcom: launched April 2013, smartphones June 2013 [2 months]
Digi: launched July 2013, smartphones XXXX 2013
Looking at the trend, it takes around 2-3 months for telco to offer smartphones after their LTE launch.
So most likely Digi will have it in Sept or Oct this year. But this is just my guess, i may be completely wrong..
Technically CSFB is required. This is a matured features that has been implemented in almost all LTE network worldwide, and supported by all LTE phones. It is just the matter of tweaking the parameters in the network and working with phones manufacturers to fit their network settings.. Again, my guess it will happen soon...
If i were you I will wait, unless if my LTE phone is iPhone5, then I will port because Digi's LTE doesn't support 1.8GHz
But it will take months before telco enable LTE-sim to prepaid customers.