Depends on certain factors.
E.g. What genre type is your video?
500,000 views in 48 hours could get you on the front page of youtube for some genres, thus, bringing another 50,000 + viewers to your video at least.
From there, you have to be honest with yourself; is the video of good content? Are people going to want to watch it?
If the answer is yes, then people, without a doubt, will share your video via other social networks, start searching for your video, & comment/ rate your video. With that, you can bring more viewers continuoulsy overtime.
Long story short, if the video content is something the average person will find entertaining, in one way or another, the 500,000 views will give you the initial boost you need, while the people of the youtube community will keep your video going after that.