You know that your computer is as fast (hardware) as it was originally.
We know it is you who demands more and more.
So you have the: Core i7” processor (2635QM)
Intel has made a nice tool for you to see what are you doing to the CPU. It even has a log function.
https://software.intel.com/en-us/articles/intel-power-gadget-20
I recommend you use it to observe how is your CPU suffering.
Also your Activity monitor will tell you that.
Why do that?
Well, it will help you making the decision if you are using 100% all the time or are there a breather periods (as observed by your fans cycles up and down. Nobody knows you better and your habits the you.
While talking about the Fans: All of your MBP is super high tech, the cooling technology is still prehistoric.

We basically use grease as heat transfer media, and a large metal block for heat dissipation, and then we use rotating blades to move the air around. Dyson has made rotator free fans (no noise) but they do not fit in to your MBP.
The Microprocessor technology is trying to reduce the heat generate by the CPU using designs and technologies (dynamic thermal management ect..) but that only goes as far. Good example is the Haswell CPU on MBA, it has much reduced power consumption (longer battery life, less heat) while delivering equal or better computing power.
So when do you get newer hardware.
Look at this: Next-gen faster Haswells chips out as soon as next month, could find their way into upgraded MacBook and iMacs.

That is next generation Haswell-refresh (core i7-4790). So it is better then the one in MacBook Air and it will stay cooler (less power consuption. Is it the right one for you? maybe! it will handle the 1000 Mb/s SSD's ? and can do this
Cores 4
Threads 8
Clock Speed 3.6 GHz
Max Turbo Frequency 4 GHz
When is Apple going to come out with it ?
If you are using the current at its max all the time that is a good indicator.
But if you are like me (limited budget) I would skip a Intel's CPU generation at least once or twice, to then get in to something it will clearly give me happiness -at least till next time :)
What can you do meanwhile while waiting:
There are lots of home remedies out there to keep your computer cooler.
Surprisingly there is one that does the best job without going insde of your Mac (it does not look pretty but who cares).
Gel- Pack Investment $15, application- set it under the MacBook Pro housing, (buy 2 so you always have a fresh one in the freezer)
Broadwell
architecture is what you need in term of heating and speed