The "role that is about to open up" line is a huge red flag. Your boss may be trying to manipulate you into staying long enough to find a replacement, now that

The "role that is about to open up" line is a huge red flag. Your boss may be trying to manipulate you into staying long enough to find a replacement, now that you're known to be "disloyal". This is why people tell you not to take the counter-offer.