According to some folks @ http://forums.hardwarezone.com.sg/showthread.php?t=2104567&page=121 that may seem to be the case. How it is being done is not certain at the moment. Some are claiming that you need to be in the Singtel Network to get the OTA. But that would not really make sense since OTA’s are done using normal internet connection (transfer of files from an ip address). The update seems to be standing at 44MB.
I think that a rooted phone is still the best road for a G1/HTC Dream phone. Why? You get to do some serious overclocking on the phone. The default maximum speed for the processor is only at 384Mhz. With software such as SetCPU (you can get it here: http://forum.xda-developers.com/showthread.php?t=505419) you can push it to the max… which is the original 528Mhz. The difference is very obvious. My phone is very stable even with this setting. No crashes, no freezes, etc.
But if you are a newbie and risk-aversed towards computers, I would suggest that you either:
1) Accept Singtel’s cupcake version and be happy with it!
2) Go to a computer shop that offers services to root it.
Why? Because Singtel is the LAST to push Cupcake 1.5 to its users in the world. Can you imagine, next month will be the release of other upgrades (like the hinted Donut), and you may not actually be able to enjoy such upgrades until 2/3 months after everyone else 🙂