This works for me, I think, though I'll accept that I could be missing some fundamental point:
IPv4_first=1.1.1.1
IPv4_second=2.2.2.2
IPv4_third=3.3.3.3
IPv4_all=( $(set | sed '/IPv4_.*[=)]/!d;s///') )
printf "'%s'\n" "${IPv4_all[@]}"
###OUTPUT###
'1.1.1.1'
'2.2.2.2'
'3.3.3.3'