Currently, when an iPhone user messages an Android user and vice versa, the chat takes place over the old-school SMS/MMS platform which is why videos shared look like crap as do shared images. Because RCS and iMessage have almost the same features, iPhone users should have no problem using RCS when Apple does add support for it.
Google says that Apple announced that RCS support on iPhone will be available this Fall
When Apple does add RCS support to the iPhone, you should be able to see whether you have an RCS connection by looking at the text field before you start typing a message. For example, after you tap on the name of the Android-using recipient you are sending a message to and you see RCS in the text field, it means that you will be chatting with the recipient using Rich Communication Services. On the other hand, if the text field says Text Message, you are messaging an Android user who doesn’t use RCS, or an RCS signal is not available. Thus, you’ll be chatting using SMS/MMS.
Apple will no doubt make a big deal about adding RCS support as it gets closer to September, so stay tuned. We can tell you that Apple’s support for RCS will not add the blue bubble/green bubble rift.