Can you guarantee that you won't misuse the port forwarding feature, and pay the entire server bill for one month if you abuse?
What kind of more guarantees do you want, @Staff just confirmed there are no plans to remove this feature, to the contrary, there are plans to look for solutions to make these resources available forever.
All other VPN providers you mention that cowardly remove this feature do not have a net neutrality prospect and mission prospect like airvpn does. If you read those, you will see p2p (not possible without port forwarding) is one of the most important aspects in a decentralized censorship-resistant internet, which is in tango with airvpn's mission. The mission and net neutrality prospects of airvpn have not changed since its inception so I doubt it will happen, unless something really ugly happens.
Happy p2p-ing in the mean time.