Exactly, like anything, it has risks and tradeoffs....U mite end up worse off or at the same place after 4 years...u mite also end up happier n more successful...but before u take up this ordeal:

1. ask urself, what u want to achieve after phd bcus most people only think it will make things better which is not necessary
2. do u have any interest in research, academia or teaching; or do u want to use it to enhance ur position in ur current area of expertize
3. better find out what kind of results do people achieve with phds in similar area

in short, find out what u want n what u can get from a Phd....dont go with wrong notions or hype...