Marc Haber wrote: > don't take the old version away until the new one is feature par and > bug free.
Leaving aside the points Philipp Kern made (some features are intentionally removed, and code is rarely if ever "bug free")... Another way of phrasing "don't take the old version away" is "someone should keep maintaining the old version", and that has the standard problems of where to find a willing "someone", *and* to what degree the maintainer of the old version can convince the community to incur the costs of continuing to support the old version. Software exists in a community ecosystem, and one person willing to maintain an alternate version of something doesn't always justify the costs the rest of the community would incur to support that alternative. That argument applies in both directions: people who do a rewrite have to convince others that their version is worth supporting, and people who want to stick with the old version have to convince others that their version is worth supporting. And the community may not be willing to support both concurrently, even if both have a non-zero number of offers of maintenance. That isn't a bug.
