IMO this is the only viable option for most open source projects with limited resources. Your users just have to switch to 1.3, which is the reasonable thing to do anyway (and soon, 1.4).
Generally, unless a package has users with very low risk tolerance, its maintainers should never hesitate requiring a released version. And conversely, users who claim they have very low risk tolerance and want to use your package on earlier versions should be ready to back this up with contributions in the form for PRs or money.