The UN is approaching a historic vote to Brexit. It is planned on June 23rd. David Cameron will have to consider in real to make the UK leave the EU, if the majority of citizens wants so in the referendum.
From the economic point of view, there is a merit for the UK to keep staying in the EU. The UK’s GDP is still expanding, but will be sluggish within some years, according to Confederation of British Industries. And Brexit is the largest factor to make investors hesitate to throw their money.
International Business Times: EU referendum: UK economy expected to slow as 'dark cloud of uncertainty' looms
If the UK leave the EU, the stock market will crash, and house price will also turn into decline, International Monetary Fund warned. This idea is shared by not only domestic but also international stakeholders. Thus, they do not want the UK to leave the EU. The US and Japan are also opposing to Brexit.
The Guardian: Brexit would prompt stock market and house price crash, says IMF
On the other hand, immigration is the most severely concerned matter in discussing Brexit. Separatists claim that staying in the EU will endanger the UK because of increased immigrants from the Middle East, many of which are refugees, and terrorists can enter the UK mimicking themselves as refugees.
Boris Johnson, the former Mayor of London, is a person on the side of Brexit. He previously compared the EU to even Hitler. He criticized Cameron for failing to keep immigration policy, and said that how many people will be accepted to the UK after Brexit depends on the economic situation. It seems contrastive to German policy to accept many refugees.
Reuters: Immigration post Brexit would depend on economy's need - Johnson
The poll regarding Brexit is quite competitive. Financial Times suggest staying is a little advantageous, but Economist’s estimation is uncertain.
Financial Times: UK’s EU referendum Brexit poll tracker
The Economist’s “Brexit” poll-tracker
The victory of Sadiq Khan, a Muslim mayor, can be a strong tail wind for the decision of staying in the EU. But, if an incident happens, the result will be easily overturned. Soon after the referendum about the independence of Scotland, British people will have to make a difficult choice again.