IANAL. I'm more familiar with GPLv3-or-later because it's how I license Red Moon, but I assume v2-or-later uses the same phrasing, which I got from the FSF website iirc:
> Red Moon is licensed under the GNU General Public License version 3 or (at your option) any later version by the contributors.
As this reads to me, I am offering you a choice of licenses. You may use Red Moon under the GPLv3, or you may choose a later version of the GPL. Or, you could choose both, if you wish to distribute your derivative as GPLv3-or-later.
Put differently, a GPLv2-or-later currently means a dual-license, under both v2 and v3 (and an automatic relicensing to triple license if v4 is released, etc).
> Red Moon is licensed under the GNU General Public License version 3 or (at your option) any later version by the contributors.
As this reads to me, I am offering you a choice of licenses. You may use Red Moon under the GPLv3, or you may choose a later version of the GPL. Or, you could choose both, if you wish to distribute your derivative as GPLv3-or-later.
Put differently, a GPLv2-or-later currently means a dual-license, under both v2 and v3 (and an automatic relicensing to triple license if v4 is released, etc).