Generally, yes. WiFi, and consequently high-speed internet, is widely available and expected at RV Parks. 50Mbps might be asking a lot, but 10+ is well within reason. Also, consider that it's shared so 30 people streaming HD Netflix might be noticeable.
Keep in mind, this if for RV Parks, which are different than what would generally be referred to as a Campground. While Campgrounds, many of which do welcome RVs, are very likely to have WiFi, speed and accessibility could be of less quality than an RV Park. Meaning, there's WiFi by office and Comfort Station/Bathhouse, but not in the remote areas.
There are also many boondocking locations which are popular, and crowded, but provide no services whatsoever.
If you're looking at specific locations, this will generally be listed under an Amenities section, but not always...go figure. Any location near to popular tourist spots will have WiFi like any nearby hotel.