I will say there is no point arguing about the word guessing because it also means prediction or speculation of which any one can guess, predict or speculates the price of Bitcoin including a trader or investor and this is a function of Bitcoin being volatile in nature. However, those trading should be nothing to be referred to as a long term trader because they don't have the ability to hold for long term hence they should be generally be called traders and not long term traders as in your post.
For context sake, it's better to use the word guessing for gamble because it sounds more like someone without directions just like casino games, while on the other hand prediction make it sounds much better because I wouldn't want to be addressed as someone who guesses the price of bitcoin, but someone who predicts or analyze bitcoin price. However I get your point but my response was based on context even if they both ment thesame thing.