Yes. In the case of a posterior vitreous separation, it is very likely to develop flashes or floaters in the other eye if you get flashes or floaters in one eye. As we know, some flashes and floaters are caused by retinal detachment. If you develop flashes or floaters in one eye, you'd better have a dilated eye exam as soon as possible.
Yes. It is very likely to develop flashes or floaters in the second eye if you get them in one eye within a year because some flashes or floaters are caused by posterior vitreous separation and retinal breaks. So you should go to see an doctor and have your eyes checked as soon as possible if you have develop them in one eye.