That's a different decision from England. The team had different plan and everything worked for them as planned. Scoring is remarkable,393 runs in 78 overs losing 8 wickets. England will now do their best to take few wickets. This could increase the winning probability of England. Lyon's bowling is really awesome, and he took 4 wickets. For Australia Moeen Ali might be a tough challenge.
It's too early to say how will Australia bat in their first session tomorrow. I understand that they have confidence behind them as they win recently against India but remember England is the host nation and they are totally different than the Indian team. Again I would not conclude anything until I see how the Aussie goes to chase this score of 393.
A lot depends upon Stuart Broad and Moeen Ali as how these two bowlers put pressure on the Australian batsmen, They would need to take wickets in order to make an impact on this match and more importantly to justify their decision of declaration.