You can absolutely have an all-electric jumbo jet RIGHT NOW... and here's why:
First off, let's pick an Airbus A380, because if we can do it with one of the largest ever commercial planes then we can do it with any plane.
Now an A380 can carry some 250 tonnes of fuel (which is nearly half the maximum take-off weight), so, provided we can build an electric jet engine that's the same size and weight as a traditional one, then you have a staggering quarter of a million kilograms to play with for the power source, cooling, motor drive electronics, 1/5th of an Olympic swimming pool...
According to this jet engine question on Quora, some 80-odd percent of the thrust of a modern high-bypass engine comes from the intake fan alone (I was a little off in my earlier comment). This means we'll need to run out electric motors 25% harder as we won't have a raging inferno to help with thrust generation as we would in a traditional engine.
Now I couldn't find much info on the weight of modern jet engine cores vs. the whole assembly but this article indicates that the intake fan section can be up to a third of the total weight, which given that the engines on the A380 are nearly 7 tonnes gives over 4 tonnes for the motor and cowling.
Thanks to this KLM blog page they recon the A380's four engines generate 230MW of power, or ~58MW per engine, but considering our need for 25% overdrive gives us ~73MW. The worlds largest electric motors are bigger than that (which in 2018 was 80MW according to GE) so we know that a suitably sized motor can be built (in fact, if you consider generators to be motors - and they kinda are - then you can get them up to at least 700MW... flying aircraft carrier anyone?)
So, we know powerful enough motors exist, we know we have ~4 tonnes to play with, so can we build an electric jumbo? Well, 73MW/4 tonnes is 18kW/kg which is definitely up there in terms of power density for an electric motor (although it's only 11% the power density of the space shuttle's rocket-powered fuel pump!). The EMRAX 268 motor already hits 11.5kW/kg so that's not too bad but not enough. Recently another company claimed to have a motor than suits our needs and if Equipmake's numbers are to be believed then 20kW/kg is doable which is perfect for what we want.
And with that, we've proved you can make an electric jet engine that's just as good as it's gas-guzzling cousins (although, given that we saved 250t on fuel because the power source weighs effectively nothing, the engine could have weight 10 times more and the plane still could have flown), given that half the cost of a flight is fuel, the airlines are going to be your new best friends as you've just come up with a way to reduce maintenance (seeing as an electric jet has only one moving part) while doubling their profits.