Potential for future price increase – Ingle Farm Adelaide

Hi Gurus

I was speaking with an agent at an open inspection this afternoon whilst having a sticky beak through a house around the corner from one of our properties and was surprised to have him advise that if our budget allows, we should hang onto the property for another 3-4 years as he believed that the area would boom around this time and that the blocks which are generally larger than those of the surrounding (newer) suburbs, will be likely subdivision targets. 

The suburb is Ingle Farm, a northern suburb in Adelaide about 13km from the CBD which has on average 650m2 blocks and 1970's double brick houses.  A couple of splits have started to be done but the double brick houses are generally in ok condition and so not many are being knocked over at this stage.

My issues were
1) Totally broadsided by an agent who knew that we were considering selling our property but didn't ask if he could come around to suggest how much it might be worth and push to try to sell it for us

2) Not quite knowing whether to believe his advice.  There was nothing for him to gain in saying what he did.

Does anyone out there have any wonderful advise about Ingle Farm, Adelaide?

Cheers
STL