armv5 target was deprecated and removed from prebuilt packages beginning with Felgo 2.8.0/Qt 5.6. You can build your app with v7a target and upload it as an update to the Google Play Store, yes. Actually we recommend to do that, as old armv5 instruction sets are probably not supported anymore on newer devices. Please keep in mind that some old devices won’t be supported by your app anymore, you can check that after uploading the new apk and checking the “supported devices” section in Google Play Dashboard.
Hope this answers your question!