and mobile applications on other platforms
Not that I necessarily agree or disagree with the expansion of these TLDs, but Google is hardly the kind of bad actor I would worry about.
The proposed gTLD will provide Google and its Network with the ability to customize domain and website name application offerings to signal to the general population of Internet users that .app websites are indeed managed by Google. The specialization goal of the proposed gTLD is to extend the Google brand and reputation to each .app second-level domain. This specialization provides a mechanism by which Google and its Network can easily link and manage their applications and related services. This specialization makes it clear to Internet users that this is the authoritative and designated space where they can find Google’s and its Network’s applications offered in association with the Google brand and accessible via differentiated and streamlined web addresses.
So all .app domains would be Google branded? That hardly bodes well for "all mobile applications on other platforms".