No. The only times when both quantum+special relativity (quantum field theory) and general relativity are both "in effect" are immediately after the big bang. IIRC the time-scale is something like 10^(-20s) after the big bang. It is only of importance in cosmology and at very high energies. Unless, of course, we're missing something...
That said, we could have asked, in the 19th century, is there any practical consequence of electricity and magnetism being the same force?
Although relativity was based on an empirical observation, Einstein is also famous for his theory predicting additional, as-yet unobserved phenomena.
From researching this thread today, I learnt that a similar thing happened when Hertz discovered radio waves: they were predicted by Maxwell's theory (which was based on an observation by Faraday):
> When Faraday discovered that a magnetic field can affect the polarization of light, he proposed in 1845 that light may be waves in the lines of force of electromagnetism.
> [...] In 1864 James Clerk Maxwell followed up Faraday's ideas with mathematical formulas that described light as waves of electromagnetism and that implied other forms of electromagnetic waves. Maxwell's work was experimentally verified in 1888 when Heinrich Hertz, following a suggestion from George Francis Fitzgerald, discovered radio waves by directly applying Maxwell's formulas.
That said, we could have asked, in the 19th century, is there any practical consequence of electricity and magnetism being the same force?