There is alot of transformation in Punggol being a newer town: Upcoming Punggol Town Hub, Upcoming NorthShore Plaza, Upcoming Sports & Recreation Hub, Upcoming Punggol Digital Hub, and many more to come. These do not include the Waterway, Waterway point and all the previous developments. All these will definitely positively impact property price when they are up, and so will Tengah Town when it matures.
However for the story of Punggol, it took over 20 years to realise since the Government announced in 1996 the Punggol 21 plan. It took so long because the construction sector was badly affected by the Asian Financial Crisis.
The issue for Tengah is that entering this BTO exercise, you will be one of the first movers for Tengah, just like entering Punggol back in 2000s. There will be a significant lack of amenities till they are up. Yes there is reward at the end of the day (JRL line, future tengah commercial central, possible LRT, many many more amenities), but will you be able to handle the inconveniences till its all done? Thats a question you must ask yourself.