Season based maps probably exists, but what we have here is not a Summer theme for hiking and winter theme for hiking.
Truth is, that winter theme may evoke using this theme for hiking in winter, which is of course not correct. Maybe some "Base theme" name should be better as it do not specify exactly usage.
As I read some discussion somewhere, guy complain about road theme and Petr suggested to use "Summer" theme with disabled hike & bike tracks. It's perfect, it's different use for this theme. And well, "summer" make no sense here. Sorry, have to agree.
@Andrew Heard: hmm broken merge, I'll check it, thanks