W_D, your TOPO! software will keep working on your computer as it is. NG has two different products with a very similar name:

TOPO! (what you and I have)
TOPO Explorer (what Gershon has)

What I expect to happen is that NG will not issue anymore upgrades to the TOPO! software and discontinue it in a few years altogether. It's been a long time since they've issued any upgrades as it is for that software, that's a pretty reliable indicator of what to expect.

When that happens it will no longer be available for newer computers, your software will still work on your current computer, but they won't sell the maps for it anymore either.

I kept a crappy computer around just to run Garmin's Mapsource software for several years. During that time I nagged Garmin often to make a Mac version of the software and to make their GPS's and mapping software to work with opensource (public domain) maps. A few years ago they finally did, but it wouldn't run on my old Mac. Works great on my new(er) "Mac Mini" now though.

Garmin's "Basecamp" software is pretty good, and you can get a bunch of free maps for it now at http://www.gpsfiledepot.com/. Actually, the maps there are a lot better than the NG TOPO! maps. They have topos with 10ft lines, public land boundaries, trails, roads, and other "layers" of data, and the data is more current.

You have to learn how to use it, which is always a pain, but at least you don't have to pay for it. And, really, we shouldn't have to pay for it a lot of it because it's all based on government data which we've all paid to collect, or data provided for free by people who went out and collected it themselves.

Companies can add value to that data, and sometimes that's worth paying for, but NG was kind of soaking us for the value they added with the TOPO! software. You can get all those quad maps for free at http://libremap.org/.

The beauty of the web based NG TOPO Explorer software was you could purchase just the quads you wanted for a buck apiece and download them when you wanted them, and it had most of the same tools that the TOPO! software does, like tools to make waypoints and routes, and they were free.

The catch was you had to prepay for a minimum number of maps. $25 got you 25 "Map Credits" (quads you could download when you wanted to). You could buy as many Map Credits as you wanted and use them when you wanted. Since it was NG, no one would have ever thought they'd just up and shut down the website with only 30 days notice and leave everyone who still had "Map Credits" out to dry, but that is exactly what they did.

Gershon's only choice is to go download a bunch of maps he may, or may not, want or ever use, and he has 28 days left to do it.

What NG could have done is give 90 days notice and double everyone's map credits. It wouldn't have cost them a dime more than what they did, and people wouldn't have felt they got left completely high and dry.