This question, or a variation of it, gets asked year after year after year.
Should you wait? There will always be a newer phone around the corner. When the S8 comes out, the Pixel 2 will be coming soon. When the Pixel 2 comes out, the S9 and G7 and Moto something and HTC whatever will be "coming soon." By the time those are available, we'll be talking about the Pixel 3. You will never have the "latest and greatest" for very long.
Do you need a new phone now? Does the S8 meet your needs and wants? Then get it. Is your current phone doing just fine? Then maybe wait until you see what the Pixel offers. Is there anything the the S8 offers that will really make your life better? If not, then wait and see.