An amazing result in number theory is that the equations shown here
http://mathworld.wolfram.com/PrimeDiophantineEquations.html
open a way to find prime numbers. It is probably very difficult to find a solution for huge $k$, but on the other hand, I see no reason, why it will not be found at some time.
How likely is that with those equations, someone finds a prime larger than any known prime ?
Has this been estimated, or has it just been stated that it will be "very difficult" to find a solution ? Theoretically, even numbers much too large for the usual primality tests could be proven prime with those equations, so it might be worth to think about this possibility.
That system of equations, even if algorithmically possible to solve, is so much non-feasible and also non-linear and have a constraint on the solutions (that solutions are positive integers) and clearly is mainly of theoretical interest.
If you would plug some very large possible prime $k+2$ into that system and would try to do the test (that is, would try to solve the system non-algorithmically) for those $26$ variables in some range to see do you have a solution in that range, even if the range is just $\{1,2,..,100\}$ the number of possible choices for all the variables in that small range is $100^{26}$.
Yes, there is some dependence of some equations on some other equations, so, some choices would not need to be checked but still, without "very fast" algorithmic method the system is practically, not non-solvable, but, not-recommended-to-solve.
Mostly the interesting part is the presence of "iff" (that is "if and only if") in the statement, meaning that primes are actually characterized by that system and its solutions, but, in order to actually find some methods for determining are some numbers of some special forms primes we would need different approaches.