I've also encountered a lot of issues with the upgrade from Crosswalk 7 to 10.
One of several problems we've had is the introduction of gpu-rasterization. Our app can't handle that and performs bad with random graphical glitches.
Another is the fact that there is a bug in Chromium 38+ which makes the Web Audio API is unavailable on certain devices running Android 4.1.2.
I contacted Google about the Developer warning regarding Crosswalk based applications, since I was a bit worried that they would start blocking apps without further notice, and this is the answer I got:
"...Thanks for contacting Google Play Developer Support about the security alert you have received with regard to using a highly vulnerable version of OpenSSL.
While it's unclear whether the issues affect every app that uses OpenSSL versions prior to 1.0.1h, 1.0.0m, or 0.9.8za, we're trying to help developers stay up to date on all security patches. Even if you think that specific issues may not be relevant, it's good practice to update any libraries in your app that have known issues. We want you to have time to update now, but eventually, to help protect users we may need to block apps that have out of date dependent libraries or other vulnerabilities.
We will provide a clear deadline before any action is taken. We don't have one to share right now, but if you are planning to update soon, that should be fine.
We recommend that you update OpenSSL as soon as possible to protect your users from the risk of compromise, and to make sure that your app is compliant with Google Play Policy on ‘dangerous products’.
We hope this helps. Please let us know if we can help you with anything else..."
It seems that the message in the Dev console is just a warning (at least for now), and that Google will provide a clear deadline for the upgrade before they start blocking apps using the vulnerable OpenSSL library.