TL;DR: Apple dominates the US smartphone market, but EU regulations may offer Android a chance for resurgence by enforcing messaging interoperability and standardizing hardware features.
Fragmentation is a huge problem for everything else. What percentage of Android users have any particular one of those apps you listed?
WhatApp is installed on little bit under 100% among all Android phones and iPhones in most EU countries and should the EU actually tackle messenger interoperability, iMessage is definitively not the main target. The most die-hard Apple fans I know use iMessage for a little bit when new features were introduced. Then they go back to WhatsApp like everybody else.
To be clear: I'm not an advocate of WhatApp here, I'm merely explaining that the EU does not care at all about Apple's chat service nobody in the EU uses. Should any legislation even affect iMessage, it'll be more coincidental, not targeted at it.