Getting out of a rut with speed.
Most guitarists who inspire to become great shredders get in this rut. Why?? An easy question to answer, it's lack of control. Most guitarists will start off at the fastest speed they can play good at, then try to move up. The biggest reason they struggle with perfecting the next level is control. The best way to better your control is too do rhythm patterns at extremely slow tempos. Most you shredders are probably thinking I'm crazy but try it. Try to actually play a solo you know perfectly at 40bpm. It's a completely different work-out which focuses on control, not speed. Somebody's quote on here said something like, "speed is nothing without control". This is absolutely true. In the end, if you work on your control along with speed exercises. You will excel to higher levels a lot quicker. I have students right now who have only been playing a year or two who can pull off pretty difficult solos that I see people with 5-6 yrs of experience having trouble with.
About being better at soloing.
Of course learn as many scales as you can. But try going through one rotation of a scale and sing each note as you play them. Up and down the scale. As you become more familiar with the scale, try singing the note before you play it. Later try jumping around the scale randomly. If you have ever seen guys who can just jump in and play exactly what they want to hear. This is the quickest way to achieve this because your memorizing the sound of each note in the scale along with the scale itself, by ear. Being a good musician is being able to play what you want to hear, right? Well there's how to accomplish that.
For those, who need to think up a solo rather quickly, a good idea is to get yourself one of those hand-tape recorders. Make yourself a loop of the rhythm parts and just hum your solo over that into the recorder. Then go back and figure out what you hummed. Of course you'll want to doctor it up, but just keep working with it until you get the entire solo down exactly how you want it. Very quick way to get solo ideas out, especially the melodic ones. This also boosts your skill of being able to pull the ideas out of your head, and as you develop; you won’t even need the recorder.
These three exercises will develop everything you need to be a better improve soloist. Control along with speed will allow you to pull off any rhythm at and tempo at will. Most importantly being able to understand what you did. Learning how to pull the ideas out of your head will allow you to improve the exactly solo note for note that you want to play at the drop of a dime. Of course this is a many year journey but it is the most effective path to follow.
"My whole life is a dark room...ONE BIG DARK ROOM" - a.f.i.