It does not really pay to second guess technology advances.

GPS and other electronics are the same this way. You will never be able to predict if the systems will improve or if they will be rendered obsolete by the next thing coming along.
GPS might be replaced by something else just like GPS has almost completely replaced LORAN-C.
(our governments still operate the LORAN transmitters but I have not heard of anybody buying new receivers lately.)

The thing with computers, radios, GPS recievers and other chip based electronics is to buy the best you can afford right now and to expect them to be obsolete within 5 years.
Sometimes they are actually obsolete the day you buy them but will take 5 years to get through the technological replacement cycle anyhow.

If you are waiting for the next great advance before you buy now then you will be still waiting for the next great advance 5 years down the road.

My GPS units are well past their replacement time as technology but they still do everything I need them to do.
The reason I will be buying a new one next year is because they are getting too old to be reliable (electronics do decay over time and repairs become unavailable)

I like the looks of the Dakota as well as the Etrex HCX, and they are not far apart in their functional abilities.
I will likely buy Dakota because it is just starting the replacement cycle, but it will really be decided by budget considerations at purchase time.
Items that are farther along the obsolescence curve tend to be priced lower even if they have the same basic features as the newer unit.