On Anet's part, it's a good idea. Even if only 5% come back and start playing again, that's 1000's of additional customers.
It may be 1,000s of additional customers, but do they pay? How long do they stick around?
It's only a good plan if they come back and spend money or continue to play and add more people to play with. Unfortunately, we will never know if that is really happening - and if the underlying causes of them leaving in the first place haven't been fixed, why would the second time around be so much different for them to stay?
What they should do is make an expansion and give those people a free 7 day trial to the expansion.